This invention relates to turbine flowmeters and, more particularly, to overspeed protection for a self-aligning probe-type flowmeter.
A turbine flowmeter has a rotatable turbine wheel positioned to intercept fluid flowing through a line. The turbine wheel rotates at a speed proportional to the fluid velocity. The rotation of the turbine wheel is sensed by a pickup coil, which provides pulses to actuate an indicator.
One class of turbine flowmeter is designed for insertion in a fluid flow line as a probe. The turbine wheel is located in a cylindrical housing suspended in the flow line from a support rod. Such a probe-type flowmeter is generally designed to disturb fluid flow as little as possible. As a result, the turbine wheel is small and is usually supported for rotation by fragile ball bearings. Rotation of the turbine wheel at a speed above that for which the flowmeter is designed may damage the fragile ball bearings.
In a prior art self-aligning, probe-type turbine flowmeter, the support rod rides on an axially extending rail as it passes through the probe casing during insertion of the turbine wheel into a fluid line. The rail controls the rotational position of the turbine wheel as it passes through the casing to insure alignment of turbine wheel with the direction of flow through the line.
An application of James F. Guthrie, entitled IMPROVED TURBINE FLOWMETER, Ser. No. 800,562, filed May 25, 1977, and an application of James F. Guthrie and Richard E. Zimmerman, entitled IMPROVED TURBINE FLOWMETER, Ser. No. 800,557, filed May 25, 1977, both assigned to the assignee of the present application, disclose arrangements for providing overspeed protection for the fragile ball bearings of a turbine flowmeter. These arrangements are not applicable to a self-aligning, probe-type turbine flowmeter wherein the rotational position of the rod supporting the turbine wheel is controlled by an axially extending rail.